Dopamine (DA) transmission within the brain has been plausibly linked to the pathophysiology of alcohol abuse, in addition other substance abuse disorders have also linked to the DA neurotransmitter. Allelic variants in the genes encoding the dopamine receptors, DA transporters and DA synthetic enzymes could predispose an individual to substance abuse. To explore this hypothesis, restriction fragment length polymorphism analysis in conjunction with polymerase chain reaction technologies have been used to genetically type individuals with substance abuse disorders. During this fiscal year, the protocol has been reviewed and expanded to allow the collection of genetic material from subjects in an unlinked manner to explore the association of these disorders with other possible genetic markers encoding DA physiology in the central nervous system.